I've been trying over the past year to shift my mindset from OO to functional and it has been tough. I'm not there 100% yet, but I can feel myself "thinking functionally" now which has been great.

I'm a .NET developer by day, so I've been looking at learning F# with a look to introducing it to the stack at work. There is a great community around F# and a wonderful learning resource is F# for Fun and Profit.

With .NET Core 2.0 released, support for F# cross-platform is also improved, so you should be able to work with it no matter what OS you're using.

FP languages are a lot more than functions being first class citizens. Its also the semantics support, syntactic support, and core language facilities. An FP language is far more than providing Filter, Map, and Reduce.

template<typenameFunction,typename...Arguments>autopartial_application(Functionfunction,Arguments...args){return[=](auto...rest){returnfunction(args...,rest...);};}autoadd6=[](inta,intb,intc,intd,inte,intf)->int{returna+b+c+d+e+f;}autopa1=partial_application(add6,4);autopa2=partial_application(pa1,5);autopax=pa2(10,11,12,13);autoc0=curry(add6);autoc1=c0(4);// sort of kind of like pa1autoc2=c1(5);// sort of kind of like pa2autocx=c2(10)(11)(12)(13);// note that c2 and pa2 are called in very different ways.// cx and pax both equal 55.

But to JavaScript you'd need to add transitive immutability (as if all objects were made deep frozen at creation, by default, using value semantics like in mathematics), piping, implicit currying, implicit partial application, guaranteed tail recursion (because of immutability),

Yes, you can do FP style programming in JavaScript. And you can also do FP style programming in C, or in C++, or in Lisp. None of those languages are FP languages.

Thanks for the response. My qualm, however, is only with the OPs mention of Javascripts function model. I am making no claims at all regarding where Javascript sits on the functional scale. Infact, I am not claiming Javascript is even a mildly good language for any type of programming. I am simply saying that functions in Javascript are first class constructs.

Maybe I've been misunderstood, but I am lost as to why that is a controversial comment.

Functions in Javascript are first-class. Period. The ability to model them as objects with instance members is not relevant. The fact that Javascript separates the notion of operators and functions does not have any relevance either. Nor does the ES6 lambda syntax. Javascript has always had first-class anonymous functions! Semantically, it's not recent at all.

The term first class is well-defined in our field. If you look it up and test each requirement against the capabilities of functions in Javascript, you will see that they are indeed first class.

This is what I usually say too, but there is no period, if you learn more advanced topics you find out that everything in JS is an object. You cannot just say is not relevant (like you say), is very relevant on THIS topic, when you compare the language to Functional Programming ones.

JS -> everything is an object
FP -> everything is a function

You can loosely say that functions are prime citizens in JS and in FP languages, but ... we have to differentiate them to a degree, world is not white and black like you say, there are many grey nuances.

In JavaScript, functions are first-class objects, because they can have properties and methods just like any other object. What distinguishes them from other objects is that functions can be called. In brief, they are Function objects. -- MDN documentation

Also Arrow (lambda called in other languages) functions are not anonymous functions, they have different implementations and effects. Anonymous is just a function without a name (which is not recommended anyway because it's harder to debug).

If you're looking for learning FP from scratch, then I'd suggest taking a look at Structure and Interpretation of Computer Programs. It's freely available as a HTML book, or you can buy a hard copy on Amazon too. SICP teaches you to write programs in Scheme which is a dialect of Lisp.

I feel like books are less helpful than actually developing something with it.

If you want to stick closer to JS, then you might look at Reason. They try to keep the syntax similar to JS, and it compiles to JS while still having all the functional goodies from OCaml. I dunno any books to recommend.

Personally, I'd recommend learning Elm (also compiles to JS). There is a book coming -- Elm in Action. For now I would learn it from the language walkthrough and then expound on that with a small project. Maybe something that your team really wants that never gets prioritized. The first time you refactor, you will be blown away by how uncomplicated the process is. Make changes, fix whatever the compiler complains about, done. So it is very forgiving with changes.

If you want to stick to JavaScript as the target environment, I recommend the programming language Elm as a good FP language.

If you don't have any particular target environment in mind, I recommend F# for .NET/Mono target, and I highly recommend Dave Fancher's The Book of F#. I've done all my F# work using the Xamarin IDE on a Macintosh.

Whatever book you find, don't get trapped in the idea that functional programming is somehow limited to certain languages. Pretty much all languages now have a lot of functional constructs -- they've become a staple of all programming..

If you are OK with a non-JS book I would recommend Functional Programming in Scala. Scala is a nice middle ground between pragmatic languages like Java and more esoteric languages like Haskell (which to purists in either camp means that it is worthless, I would disagree).

This book specifically does a good job introducing Scala and motivating FP concepts.

Kyle Simpsons Functional Light JS is not yet finally released, yet the draft is complete; this one I haven't read yet, but judging from his "You don't know JS" book series, I recommend his writings blindly ;)